The present invention relates to an optical device for use in wavelength-division multiplexing (WDM) techniques; and, more particularly, to an optical communication device, for multiplexing and demultiplexing various wavelength, employing a Fabry-Perot filter which has a novel structure achieved by using a silicon micromachining process.
In general, WDM techniques provides means for multiplexing, i.e., combining, multiple optical sources of different wavelengths for coupling into a single optical fiber for simultaneous transmission and means for demultiplexing, i.e., separating, the different wavelengths for detection by optical receivers, wherein each of wavelength loads large amount of information. In WDM techniques, a channel generally incorporates therein 64, 128 or more wavelengths with 0.8 nm (100 GHz) of a wavelength separation. Recently, it is provided dense wavelength-division multiplexing (DWDM) techniques utilizing a channel including wavelengths with 0.4 nm (50 GHz) of a wavelength separation in order to obtain more channels.
In the forgoing optical communication, one of necessary optical device is an optical filter having an accurate wavelength-resolution. Conventional optical filters are fabricated by a way of alternately stacking or depositing tens of dielectric layers having a high refractive index and a low refractive index.
Refractive index difference between two alternating layers should become large so as to obtain a high separation for transmitted wavelengths and a reduced crosstalk between adjacent wavelengths. Two materials that can be used up to now and will give the largest refractive index difference therebetween are silicon (a refractive index of 3.48 at the wavelength of 1550 nm) and air (a refractive index of 1).
Conventional optical filters incorporating therein multiple laminated layers for use in an optical communication device such as multiplexer, demultiplexer (MUX/DEMUX) are disclosed in U.S. Pat. Nos. 5,808,763, 6,008,920 and 5,737,104. In the above disclosures, a multilayered filter is formed on a substrate. When various wavelengths are incident upon the multilayered filter with a specific incidence angle, various wavelengths are separated from each other by a repetition way of that one wavelength is transmitted to outside and the other wavelengths are reflected within the multilayered filter with a changed incidence angle. In other words, the multilayered filter separates various wavelengths into each other with a wavelength transmission property determined with respect to the incidence angle.
Other conventional filter disclosed in U.S. Pat. No. 6,122,417 is provided with a linear array of Fabry-Perot resonators, each of the resonators transmits a wavelength, and includes an improved mirror surface and optical fibers.
When the optical fibers are arranged to a structure formed on a wafer, since the optical fibers are perpendicular to the structure, packaging between the optical fibers and the structure cannot be achieved by using a batch process, thereby requiring additional equipments for arranging the optical fibers and hence making the manufacturing process thereof be complex.
Furthermore, the structure includes multiple layers deposited on the wafer, wherein the number of layers should be increased so as to obtain higher reflective mirror, resulting in increasing the manufacturing cost thereof.
It is, therefore, an object of the present invention to provide an optical tunable filter capable for use in an optical communication device.
It is another object of the present invention to provide an optical communication device for demultiplexing various wavelengths by using an array of optical tunable filters.
It is still another object of the present invention to provide an optical communication device for multiplexing various wavelengths by using an array of optical tunable filters.
In accordance with one aspect of the present invention, there is provided an optical tunable filters comprising: a fixed mirror including a number of first erecting plates; a movable mirror including a number of second erecting plates; an air gap disposed between the fixed mirror and the movable mirror; and an actuator reciprocating the movable mirror for changing the width of the air gap.
In accordance with another aspect of the present invention, there is provided an optical communication device for demultiplexing various wavelengths, comprising: an input optical fiber; a number of output optical fibers; and an array of optical tunable filters, wherein each of the optical tunable filters is regularly arranged to correspond to one output optical fiber, each of the optical tunable filters including: a fixed mirror including a number of first erecting plates; a movable mirror including a number of second erecting plates; an air gap disposed between the fixed mirror and the movable mirror; and an actuator reciprocating the movable mirror for changing the width of the air gap.
In accordance with still another aspect of the present invention, there is provided an optical communication device for multiplexing various wavelengths, comprising: a number of input optical fibers; an output optical fiber; and an array of optical tunable filters, wherein each of the optical tunable filters is regularly arranged to correspond to one input optical fiber, each of the optical tunable filters including: a fixed mirror including a number of first erecting plates; a movable mirror including a number of second erecting plates; an air gap disposed between the fixed mirror and the movable mirror; and an actuator reciprocating the movable mirror for changing the width of the air gap.